Could someone please tell me what kind of Myriophyllum is this?
This one was sold as "Myriophyllum mattogrossense", but I don´t think it is correct. Sorry I don´t have more information.I don't think anyone could more than guess based on just the photos. Origin, leaf details, perhaps even flowers , etc are likely needed. The ones commonly seen in the hobby are one thing, but there are so many of them that if you collected something new or imported a new one with no species name, it could be pretty difficult (we tend to accept new names attached to plants as valid unless proven otherwise unless it's obviously way off).